Quadrature modulation and demodulation schemes allow two message signals to be conveyed on a single carrier wave. The two message signals are usually out of phase or phase shifted by about ninety degrees. In a quadrature receiver, the two message signals can be retrieved from a received signal. For example, the quadrature receiver may include separate receiver paths, one of the receiver paths applying a phase shift to the received signal. The resulting signals are generally referred to as the ‘I’ (real) and the ‘Q’ (phase shifted) signals.
The I/Q signals are processed using different components along the separate receiver paths. Differences in the components used as processing applied to the I/Q signals can create an imbalance in between processed I/Q signals. For example, components along the I/Q paths may have different gain or frequency parameters. Additionally, due to hardware tolerances the phase shift applied to the Q signal may not be exactly ninety degrees. The differences along the I/Q paths creates self-imposed interference or distortion in the resulting signal. The distortion in the resulting signal raises the noise floor in baseband signal processing, which may result in signal loss and/or increased processing complexity.
Different I/Q imbalance compensation schemes attempt to reduce this self-imposed interference or distortion in different ways. However, current I/Q imbalance compensation schemes suffer from one or more of the following problems: 1) narrowband, 2) static, fixed compensation, 3) data/tone aided training, 4) not programmable, and/or 5) analog.
Therefore, there is a need for an improved I/Q imbalance compensation scheme. In particular, there is a need for a quadrature receiver that is capable of digital programmable adaptive wideband I/Q imbalance compensation.